Clearbit's transition from dokku-alt to CoreOS/Fleet for managing services highlights their evolution in handling service deployments on Amazon's EC2. Initially, dokku-alt served well for small-scale applications but lacked the capability to efficiently manage multiple service instances on a single machine, leading to cumbersome deployments and configuration updates across multiple machines. As service demands increased, Clearbit explored alternatives and opted for Fleet due to its simplicity, flexibility, and the robust reputation of the CoreOS team. Fleet, which operates as a clustered layer over systemd, leverages etcd for distributed configuration management, allowing seamless configuration changes across clusters and enabling multiple service instances through systemd unit file templates. This shift facilitated more efficient management of services, including Docker-based deployments, environment variable handling, and coordination across instances, ultimately leading to the development of the tool "fluster" to streamline configuration and deployment processes. Fluster enhanced their deployment strategy by allowing the simultaneous running of multiple application versions, enabling smoother testing and rollback procedures.